Fully-Loaded Firefox
Mozilla Firefox is an excellent browser by itself, but what really sets it apart from IE, Opera, or Safari is how easily it can be customized with themes and extensions. When Firefox is properly configured, it eats all the others for breakfast, but remembering which extensions to get can be a pain, so I've made this handy guide.

Theme
Qute by Arvid Axelsson(jar)
The best theme I've seen, by far. Simple, elegant, and fun designs that are easy on the eyes and easy to use.

Extensions

Adblock Plus(xpi)

Removes advertising from web pages, cutting download time, saving bandwidth, and removing distracting clutter from your web browsing experience. The Plus version includes whitelisting for better control.

Adblock Filterset.G Updater(xpi)

Automatically synchronizes your Adblock filter set with Pierceive's comprehensive Filterset.G list.

CustomizeGoogle(xpi)
Allows you to have links to competing search engines automatically inserted in your Google results, filter specific sites from all search results, block Google's tracking cookie (if you're paranoid), remove Google's text ads, and a bunch of other options.

FasterFox(xpi)
Adds several performance-enhancing tweaks to Firefox.

FLST(xpi)
That stands for Focus Last Selected Tab. If you have multiple tabs open and close one, focus goes to the next most recently viewed tab. This makes sense because it is the way Windows treats closing programs.

Google Toolbar(install page)
Superior to the default search box in Firefox- for each search term, a button is automatically created which will automatically find the next instance of that term in the current document. Also highlights search terms, checks spelling in forms, automatically links addresses to Google Maps, fills out forms, etc. Also try the Google Web Accelerator, Google Safe Browsing(xpi), and Blogger Web Comments(install page) extensions.

greasemonkey(xpi)
Allows one to use custom javascripts to automatically modify specific pages after they are downloaded. Write your own scripts, or download from userscripts.org. Great for removing annoying elements from sites, bypassing ad pages, extracting video links, and other useful hackery.

IE Tab(xpi)
Eliminates the need to ever open an IE window again. Allows you to load sites in IE within a Firefox tab, and set specific sites to always load in IE. Great for those few luddite sites that refuse to comply with standards and work on anything other than IE.

SessionSaver(xpi)
Remembers what tabs you had opened whenever Firefox is closed and reopens them the next time you open Firefox. A lifesaver in the event that you accidentally close the window in the middle of a deep browsing session.

Tabbrowser Preferences(xpi) Adds a whole bunch of new options to the "Tabbed Browsing" options under Tools > Options. Particularly useful is the fact that you can make Firefox open links in new tabs whenever you middle-click (push down on wheel) on them. You can also close tabs by middle-clicking on them.


Icon Bookmarks
One of the things I really like about Firefox is that it actually uses sites' Favicons wherever possible. One trick I've learned is that you can delete bookmark text entirely if the site has a Favicon, and you can place them up by the menu bar. Here's how:

First you want to make sure the bookmarks toolbar is turned on. You can do this by right-clicking on the menu bar and checking Bookmarks Toolbar.

Next, you want to go to Customize... on the same menu.


When the Customize Toolbar menu is open, the contents of the Bookmarks toolbar are replaced by an icon labeled Bookmarks Toolbar Items. Drag this icon to the space next to Help on the menu bar.


It should now look like this. Close the Customize Toolbar menu and hide the Bookmarks Toolbar. The bookmarks themselves will stay.


Now, say we want to create a link for the BBC. If we go to the BBC's website and drag the URL to where our bookmarks are stored, we'll have a bookmark.



If we click on the bookmark, once it has reloaded it will pick up the Favicon




Now we right-click on the bookmark and go to properties.












Clear the contents of the Name field for the bookmark and click OK.














Voila! Now you have an icon bookmark. If you have Tabbrowser Preferences installed, you can then simply middle-click on the icon to open that site in a new tab.